Three-piece, wound golf balls with balata covers are preferred by most expert golfers. These balls provide a combination of distance, high spin rate, and control that is not available with other types of golf balls. However, balata is easily damaged in normal play, and, thus, lacks the durability required by the average golfer.
In contrast, amateur golfers typically prefer a solid, two-piece ball with an ionomer cover, which provides a combination of distance and durability. Because of the hard ionomer cover, these balls are almost impossible to cut, but also have a very hard "feel", which many golfers find unacceptable, and a lower spin rate, making such balls more difficult to draw or fade. The differences in the spin rate can be attributed to the differences in the composition and construction of both the cover and the core.
Many attempts have been made to produce a golf ball with the control and feel of a wound balata ball and the durability of a solid, two-piece ball, but none have succeeded totally. For example, cover compositions made with low flexural modulus ionomer resins provide improved spin and feel characteristics, but have a relatively low initial velocity that results in a shorter overall distance.
Golf balls having a non-wound intermediate layer between the cover and the core have also been disclosed. For example, U.S. Pat. No. 5,253,871 to Viollaz discloses the use of at least 10 percent of a block copoly(amide-ether) elastomer, optionally blended with an ionomer, for use as the middle layer of a three-layer golf ball. The hardness of the block copolymer is said to be within the range of 30-40 Shore D hardness, while the corresponding hardness of the ionomer component is said to be between 55-65 Shore D. The overall hardness of the middle layer is said to range from 20-50 Shore D. The cover may also be a block copoly(amide-ether) and ionomer blend but its overall hardness must be greater than that of the adjacent middle layer.
Consequently, a need exists for a golf ball composition that provides spin rates and a feel more closely approximating those of balata covered balls, while also providing the distance of an ionomer covered two-piece ball and a degree of durability as high or higher than that provided by the balls presently available or disclosed in the prior art.